Some electrostatic air cleaners utilize an electrical potential difference between spaced collector electrode plates and driver electrode plates to facilitate particle deposition on the collector plates. For efficient collection of particles from air, a high potential, usually 10 kV to 30 kV, is applied between the collector plates and insulated driver plates. The use of such high potentials creates the risk of damaging arcing between components at different potentials and necessitates additional steps in the manufacture and maintenance of the device. For example, the contact points, i.e. the portions where electrical connections are made between different components, particularly insulated components, must be properly shielded.
While a proper insulation will adhere well to the driver plates, problems tend to occur in the electrical contacts joining the insulated drivers to their source of electrical potential. At those contact points, the insulation on the insulated drivers and the insulation on connecting conductors are opened in order to make the contact. If the contacts are left unshielded, the contact points must be far enough from the collector plates, i.e. the creeping distance between those contacts and the collector plates will have to be sufficient, to avoid arcing. The term “creeping distance” is used herein to indicate the distance between the two closest points on the surface of the insulated structures of oppositely charged components. Additionally, particles initially entrained in the air, e.g. dust and dirt, particularly when combined with high humidity, will collect on one or more of the plates and can shorten the effective “creeping distance”. In other words, the particles which accumulate along and around areas where the creeping distance is minimal can form a conductive path between the opposed conductors. Electrical shorts and arcing can result and cause irreversible damage to the device.
To make the design compact and reliable, and with the exception of a single point on each driver electrode for a plug or socket for the input of the required potential, the contact points on insulated driver electrodes are commonly shielded with epoxy. However, many good insulators such as polyester and Teflon do not bond very well with many epoxy materials. As the epoxy and the insulator are subjected to mechanical shocks and/or temperature variations, over time small cracks tend to develop in the bonds. Water can be trapped in those cracks during washing processes. When the cracks propagate, the water will short the shielded contact. If the distance between the openings of the cracks and the collector plates is less than the distance required to avoid arcing, i.e. the arcing distance to the collector plates, arcing will occur and the collector module can be irreversibly damaged. Even when the distance between the openings of the cracks and the collector plates is longer than the arcing distance to the collector plates, their creeping distances will usually be rather small and do not provide stable operation since the accumulation of some moist dirt/particles can lead to arcing across the driver electrodes and collector plates. Moreover, the bond of the epoxy to the insulator will often degrade very quickly if it is subjected to dishwasher treatment.